1. Field of the Invention
Embodiments of the present invention relate to center pivot irrigation systems that include a corner unit. More particularly, embodiments of the present invention relate to guidance control systems for controlling the route followed by corner units of center pivot irrigation systems.
2. Description of the Related Art
Center pivot irrigation systems are typically used for crop irrigation and generally include a pipeline connected to a fluid source, a plurality of towers, and a plurality of mechanical drive units. The fluid source may be a tank, a well, or a similar source that has a fixed location. The pipeline may include a plurality of fluid-spraying sprinklers distributed along its length, wherein one end of the pipeline is rotatably coupled to the fluid source. The towers generally support the pipeline and are spaced apart such that several sprinklers are located between each tower. The mechanical drive units may include an electric motor or a similar source of propulsion. Each tower may also include one or more wheels that are fixed in orientation and driven by a mechanical drive unit. In general, the mechanical drive units propel the towers and the pipeline around the fluid source to provide crop irrigation over a circular area.
When the boundaries of the crops to be irrigated are irregular or non-circular, an extendable corner unit may be added to the free end of the pipeline to more fully irrigate the irregular or non-circular area. The corner unit may include additional pipeline and sprinklers as well as at least one tower with a mechanical drive unit and one or more wheels that are steerable. Typically, an overhang portion of the pipeline and sprinklers extends outward beyond the tower. Thus, it is likely that there are crops located on the inward side of the tower (toward the fluid source) and the outward side of the tower (away from the fluid source). Accordingly, there may be a path for the wheels to follow that includes crops on both sides of the path. Therefore, the wheels need to be guided with precision in order to optimize the efficiency of the irrigation and avoid damage of the crops by the wheels.